Abstract This SBIR Phase II proposal is designed to advance the progress made during the SBIR Phase I project ?Robust Small Animal Oxygen Imager to Model Enhanced Cancer Treatment?. During Phase I, we have developed a prototype of robust oxygen imager, JIVA-25, for preclinical cancer biology and radiation therapy research. In the current proposal, we plan improvements in hardware, software, and image acquisition methodology that will lead to reduced instrument weight, better instrument performance, and higher resolution oxygen maps. In addition, we will evaluate the JIVA-25 performance with cancer research animal studies that use radiation therapy and drug application. JIVA-25 is a 25 mT oxygen imager with small footprint based on the principles of electron paramagnetic resonance oxygen imaging. JIVA-25 can provide oxygen maps in tissues with 1 mm spatial resolution, 1 torr oxygen resolution and 1-10 min temporal resolution. No other competing method can provide accurate noninvasive pO2 maps with such precision. In tumor, accurate real-time pO2 maps will lead to oxygen guided radiation therapy (OGRT). OGRT is expected to reduce the delivered high radiation dose volume by lowering the dose to well-oxygenated tumor tissues. This will preserve the structure and integrity of irradiated tissues and reduce radiation side effects. The absence of preclinical (animal) oxygen imaging data is the major impediment in the development of evidence base for OGRT translation into clinics. The availability of oxygen maps in preclinical settings is also expected to lead to advanced drug and radiation therapies. Providing the research community with JIVA-25 instrument is the first step in achieving these goals.